This invention relates to an optical recording medium for optically recording and reproducing the information and, more particularly, to an improvement in the optical recording medium in which an organic dye is used as a recording material.
The optical recording medium for recording and reproducing the information based upon irradiation of a laser beam usually includes a recording layer of an optical recording material formed on a substrate. The recording of the information is by condensing the laser light on the recording layer for forming pits, while the reproduction of the information is by detecting the difference in reflectance between an area in which pits are formed and an area in which pits are not formed.
Such optical recording medium is attracting attention as a recording medium for storage of a large quantity of the information, since it is possible to render the track width narrower than that of the magnetic recording medium and hence the high-density recording becomes possible. For this reason, investigations are proceeding briskly for improving the volume of the recording information.
The red to infrared laser light is generally employed for recording/reproducing the information on the optical recording medium, and a recording medium adapted therefor has become popular. Also the disc-shaped recording medium allowing data recording by the user, such as CD write-once or CDWO, has made its debut.
Meanwhile, in the CDWO, the recording laser light beam has a wavelength equal to that of the replay laser light beam. However, if reproduction is continued for a prolonged time, there is the risk of destruction of the recording pits by the replay laser beam or optical deterioration of the material of the recording layer.
In addition, such recording medium is low in sensitivity and is not suited for high-speed recording/reproduction.
If, in the case of a recording medium in which the laser light beam of the red to infrared region is used for recording/reproduction, so-called ultra-resolution or the like technique is required for increasing the volume of the information recorded per unit area of the recording medium.